The present invention relates to a gas cushioned free piston type engine with two oppositely arranged combustion cylinders, the pistons of which are rigidly connected by a common piston rod. The engine includes further a hydraulic pump cylinder arranged in a central part of an engine with a pump piston, the opposite faces of which are impingeable by fluid, and which is fixed on the aforementioned common piston rod, and a common suction chamber as well as a common pressure chamber, which, together with suction and outlet valves for the two pump sylinder chambers, are arranged in a central part of the engine located between the two combustion cylinders.
A gas cushioned free piston type engine of the aforementioned kind is already disclosed in the U.S. Pat. No. 3,089,305. This engine has, as compared with other engines of the aforementioned type, as for instance disclosed in DT-OS 1,576,890, the advantage that practically all control devices are concentrated in a center part of the engine. It has already been proven that the commercial use of such engines, which operate with high compression and high efficiency and which have the essential advantage not to require a crankshaft, will decisively depend on how compact and reliable in operation such a machine may be produced.